SQL query to get value after four _ symbols

Question

Hi,

I am trying hard to get one value from database.

my database value is some thing like

yxmn_euheiu_uhfi_jdfhf_A6_hfurh
dsfsdgdf_dsgrgrd_rshrfhfd_hsdsg_B5_Dgsdgd_asgsgsd



My output should only A6, B5 values from database.

A6, B5 gets only after four "_" symbols. 

Please help me to write sql query.

Darma